The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for patterning a metal line with a titanium/titanium nitride (Ti/TiN) barrier metal layer.
In recent years, with the integration of bit lines, a single or multiple layers formed of Ti and/or TiN is typically used as a barrier metal layer for the bit line. When, however, employing the Ti/TiN as the barrier metal, there exists a limitation that a portion of the barrier metal layer is lost, and resultantly the bit line collapses, while performing a cleaning process after etching a tungsten layer and the barrier metal layer.
FIGS. 1A and 1B are cross-sectional views illustrating a typical method for patterning a bit line. Referring to FIG. 1A, a barrier metal layer, a tungsten layer and a hard mask nitride layer are sequentially formed over an oxide layer 11 which has undergone predetermined processes. Then, an etching process is performed using a bit line mask to thereby form a bit line pattern configured with a barrier metal pattern 12, a tungsten pattern 13 and a hard mask nitride pattern 14. Thereafter, referring to FIG. 1B, a cleaning process is performed for removing by-products produced in the etching process.
Meanwhile, prior to the cleaning process after the dry etching process, the structure with the bit line pattern formed is inevitably exposed to an ambient atmosphere for a predetermined duration. Accordingly, the Ti/TiN barrier metal pattern 12 exposed to the ambient atmosphere reacts with oxygen contained in the atmosphere so that side surfaces of the barrier metal pattern 12 are oxidized. This oxidized portion 15 of the barrier metal pattern 12 is removed during a subsequent cleaning process, which causes a thickness loss of the barrier metal pattern 12. Moreover, the thickness loss of the barrier metal pattern 12 weakens the bearing power at the lower part of the bit line pattern, i.e., at the barrier metal pattern 12. After all, the bit line pattern may collapse. Unfortunately, the pattern collapse phenomenon is not limited to the patterning process of the bit line but also occurs during a patterning process of a metal line using Ti/TiN as a barrier metal.